The Reticuloendothelial System (RES) is a complex network of cells, tissues, and organs, including the liver, spleen, and lymph nodes, that work together to remove harmful substances from the body. There are several synonyms for the RES, including the Mononuclear Phagocyte System (MPS), the Mononuclear Reticuloendothelial System (MRES), and the Macrophage System. The MPS refers to the cells that make up the RES, including monocytes and macrophages. The MRES emphasizes the involvement of the reticular cells in the system, while the Macrophage System highlights the role of macrophages in removing foreign substances. These terms are often used interchangeably and demonstrate the interconnectedness of the immune system in maintaining overall health and well-being.